Limiting reagent is the reactant which is used up completely in the reaction. Here, let’s find the way to identify it in basic concepts of Chemistry.
What is Limiting reagent ?
The reactant which is used up completely in the reaction is called L.R.
For example: A + B2 ➡️ AB2
a) If 2 mol of A reacts with 3 mol of B, then find out the LR.
2 moles of A will reacts completely with 2 moles of B. Hence, A is the L.R.
b) If 5 mol A + 2.5 mol B, then find the L.R. ?
2.5 moles of B will react with 2.5 moles of A. Hence, B is the L.R.
What is Excess reagent ?
The excess reagent is other than L.R. It is present in excess and not used up completely in the reaction.
A + B2 ➡️ AB2
a) If 2 mol of A reacts with 3 mol of B, then find out the LR.
B is present in excess. Hence, it is the excess reagent in this reaction.
b) If 5 mol A + 2.5 mol B, then find the L.R. ?
A is present in excess. Hence, it is the excess reagent in this reaction.
Identify the L.R. and E.R. in the following reaction ?
6H2 + 4 Cl2 ➡️ 8HCl + 2 H2
Answer : Cl2 is used up completely in the reaction. Hence, it is L.R. And H2 is the excess reagent. H2 molecule remains after the reaction. See the diagram below:
FAQ’s related to Limiting Reagent
- What is the difference between L.R. and E.R. ?
Answer : The reactant which is present in less amount is called L.R. The other reactant is excess reagent.
2. What is the difference between reactant and reagent ?
Answer : The substance is used up in the reaction is called reactant. The substance which starts the reaction is the reagent.
Check out the structure of NH3 here
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